HST Ultraviolet Spectroscopy of NGC 1741- a Nearby Template for Distant Energetic Starbursts

Abstract

We have obtained a Hubble Space Telescope ultraviolet image and spectrum of the nearby Wolf-Rayet galaxy NGC 1741. The spatial morphology from the Faint Object Camera image is dominated by two main starburst centers, each being about 100 times as luminous as 30 Doradus. Both starburst centers are composed of several intense knots of recent star formation. A Goddard High Resolution Spectrograph spectrum of a portion of the southern starburst center is consistent with a population of young stars following a Salpeter IMF for masses above approx 15 Msun (lower mass stars may also be present), and extending up to approx 100 Msun; about 10^4 O-type stars are inferred from the UV luminosity. Numerous strong interstellar lines are detected. Although not resolved, their strength suggests that they are formed in individual bubbles and shells with velocities up to a few hundred kms. The red wing of the Lyman-alpha absorption profile indicates the presence of several neutral hydrogen components, one in our own Galaxy and the others at or close to the distance of NGC 1741. Overall, the stellar and interstellar line spectrum, as well as the continuum shape of NGC 1741, strongly resembles star-forming galaxies recently discovered at high redshift.